I ran into an issue while changing a database schema around. Some queries
still worked, even though I didn't expect them to.
Can anyone explain to me why the following is valid (running 9.6) ?
schema
CREATE TEMPORARY TABLE example_a__data (
foo_id INT,
bar_id INT
);
CREATE TEMPORARY TABLE example_a__rollup_source (
id int primary key,
name varchar(64),
foo_id INT,
check_bool BOOLEAN
);
CREATE TEMPORARY TABLE example_a__rollup AS
SELECT id, name, foo_id
FROM example_a__rollup_source
WHERE check_bool IS TRUE
;
query:
SELECT foo_id
FROM example_a__data
WHERE foo_id IN (SELECT bar_id FROM example_a__rollup)
;
a raw select of `SELECT bar_id FROM example_a__rollup;` will cause an error
because bar_id doesn't exist
postgres doesn't raise an error because example_a__data does have a bar_id --
but example_a__rollup doesn't and there's no explicit correlation in the query.
can someone explain why this happens? i'm guessing there is a good reason --
but I'm unfamiliar with the type of implicit join/queries this behavior is
enabling.
